U.S. Secretary of State John Kerry visited the revered memorial to Hiroshima's atomic bombing on Monday, delivering a message of peace and hope for a nuclear-free world seven decades after the United States used the weapon for the first time in history.

Kerry became the most senior American official ever to visit the site, touring the city's Peace Memorial Park and Museum with other foreign ministers of the Group of Seven industrialized nations. Some 140,000 Japanese died in the attack in the final days of World War II.

Honored to be 1st Sec State to visit Hiroshima Peace Memorial Museum & Park. Here is what I wrote in the guestbook. pic.twitter.com/suQSxMCLs1

Shortly before the scheduled event, Kerry called it "a moment that I hope will underscore to the world the importance of peace and the importance of strong allies working together to make the world safer and, ultimately, we hope to be able to rid the world of weapons of mass destruction."

"And while we will revisit the past and honor those who perished, this trip is not about the past," Kerry told Japanese Foreign Minister Fumio Kishida, a Hiroshima native. "It's about the present and the future particularly, and the strength of the relationship that we have built, the friendship that we share, the strength of our alliance and the strong reminder of the imperative we all have to work for peace for peoples everywhere."

Kerry's appearance just footsteps away from Ground Zero further marks an evolution for the United States, whose leaders avoided the city for many years because of political sensitivities.

No serving U.S. president has visited the site, and it took 65 years for a U.S. ambassador to attend the city's annual memorial service. Some Americans believe the dropping of atomic bombs on Hiroshima on Aug. 6, 1945, and on the Japanese city of Nagasaki three days later were justified and hastened the end of the war.

Nevertheless, Japanese survivors' groups have campaigned for decades to bring leaders from the U.S. and other nuclear weapon states to see Hiroshima's scars as part of a grassroots movement to abolish nuclear weapons. And they've never pressed for an apology from the United States.

A senior U.S. official traveling with Kerry said the top American diplomat wouldn't issue an official apology. But he said Kerry would express the sorrow that all feel upon reflection about the bombing and use the occasion to promote President Barack Obama's vision of nuclear disarmament. The official wasn't authorized to be quoted by name on Kerry's plans and demanded anonymity.

Obama himself may travel to the city next month.

The official said that the president has yet to decide whether he might visit Hiroshima and the memorial when he attends a Group of Seven meeting of leaders in central Japan in late May, according to the official. During his first year in office, Obama said he would be "honored" to do so.

As Kerry toured the museum, some 800 schoolchildren waited for him at a cenotaph monument in the middle of the adjoining park. They held flags of the G7 nations, including the United States.

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